In the case of conventional surface-mountable optoelectronic components, first of all a pre-housed device is produced by encapsulating a prefabricated leadframe with a suitable plastics material by injection molding, said plastics material forming the housing of the device. Said device has a depression or recess for example at the top side, into which depression or recess leadframe terminals are introduced from two opposite sides, a semiconductor chip such as an LED chip, for example, being adhesively bonded and electrically contacted on one leadframe terminal. A clear radiation-transmissive potting composition is then filled into said recess. This basic form of surface-mountable optoelectronic components is disclosed for example in the article “SIEMENS SMT-TOPLED für die Oberflächenmontage” [“SIEMENS SMT-TOP LED FOR SURFACE MOUNTING”] by F. Möllmer and G. Waitl, Siemens Components 29 (1991), issue 4, pages 147-149.
In the case of these known surface-mountable designs, a highly directional radiation can be achieved by the sidewalls formed by the plastic housing being formed as inclined reflectors. Depending on the form of housing or form of reflector, the component may be constructed as a so-called toplooker, i.e. with a main radiating direction essentially perpendicular to the mounting plane of the component, or as a so-called sidelooker, i.e. with a main radiating direction essentially parallel or at an acute angle with respect to the mounting plane of the component. Examples of a toplooker and of a sidelooker with the corresponding forms of housing are shown for example in FIG. 2 and FIG. 3, respectively, of U.S. Pat. No. 5,035,483 A1.
Various conventional designs of optoelectronic components of the type mentioned in the introduction are illustrated diagrammatically in FIGS. 12 to 15.
In the case of FIG. 12, the semiconductor chip, such as an LED chip, for example, is incorporated in a narrow housing or basic body. In this housing, the beams emitted to the side by the semiconductor chip are reflected back onto the side areas of the semiconductor chip again by the basic body's sidewalls formed as reflectors and are absorbed, so that radiation is lost there.
In the case of the construction of a conventional optoelectronic component as illustrated in FIG. 13, a loss of light in the component is caused in particular by the special chip technology, in the case of which a large proportion of the emitted radiation is radiated obliquely rearward from the semiconductor chip. A substantial part of this radiation that is emitted obliquely rearward is absorbed by the basic body and lost.
FIGS. 14A and 14B show a side view and plan view, respectively, of a basic body in which a plurality of LED chips are incorporated in order, for example, to be able to generate arbitrary colors by mixing three primary colors. In this case, part of the radiation emitted laterally by the LED chips is absorbed by the side areas of the adjacent LED chips, as a result of which radiation is lost.
Finally, there are also known optoelectronic components whose basic body is made dark, as is illustrated in FIG. 15A. This embodiment is used, for example, in order to achieve a best possible contrast between the emission area of the component and the rest of the apparatus area, as can be discerned in FIG. 15B. Such a contrast improvement is used for example in indication or display technology. The dark housing has the disadvantage, however, that a certain proportion of the light emitted by the LED chip is absorbed at the dark sidewalls of the recess, as a result of which the luminous efficiency is reduced.
Moreover, especially in the case of components having a plurality of LED chips, as are shown for example in FIG. 14, a light emergence from the emission area of the component is produced which is nonuniform and acts in an off-center fashion. In addition, the plurality of LED chips are necessarily not all arranged in centered fashion, so that, when the component is observed laterally, the light emissions of the individual LED chips may be important to different extents and thus, for example, the color mixing in the case of multicolor LEDs becomes angle-dependent from a certain degree.
On account of the clear radiation-transmissive potting composition, the LED chips and the wirings thereof can in part be distinguished from short distances. Particularly in the case of a narrowing of the radiation characteristic in order to achieve a higher luminous intensity, the chip surface is projected onto the emission area of the component. Furthermore, in the event of incidence of extraneous light, a deficient contrast is produced as a result of the extraneous light reflected at the emission area and the chip surface.
In order to avoid the abovementioned disadvantageous phenomena such as low efficiency, disturbing projections of the chip surfaces and wirings, nonuniform light emission and contrast deficiency, at the present time use is made for example of optoelectronic components which achieve a higher efficiency through higher-quality and thus also more cost-intensive chip technologies in the case of which, in particular the LED chips principally emit light via the chip surface.
For applications in the field of indication or display technology, in which a good contrast during the light emission is important, the prior art discloses, on the one hand, making the component surface dark, as is indicated in FIG. 15B, or using upstream diaphragm apparatuses in order to shade the LED chips from incidence of extraneous light.